Method for overhead submerged arc welding and apparatus to implement the same

ABSTRACT

The invention relates to technology and equipment for arc welding. 
     A method of overhead submerged arc welding consists in that flux at the  wing site is pressure-fed to the joint being welded from below at different pressures along the joint being welded, a consumable electrode (3) is fed through the flux (3) from below and an arc is struck. A weldpool is formed thereat with a layer of liquid slag. The joint is welded by feeding the flux (A) on the section (A) before the arc relative to the weld being formed under a constant pressure, needed to provide conditions for pressuring the weldpool, and on the section of the arc burning and the weldpool location pressure is exercised through a layer of flux and a layer of liquid slag, the bulk of the flux being pressure-fed to the zone of the weldpool formation and the pressure gradually built up in a manner that its maximum value is distributed along the boundary of the section of the beginning of the weld solidification and maintained constant all along the boundary of solidification. Then solidification is effected and the weld is formed. 
     There is also proposed an apparatus to implement the method. 
     The invention may be used for welding longitudinal and circumferential rotatable joints.

FIELD OF THE INVENTION

1. Background of the Invention

The present invention relates to arc welding, and more specifically, toa method for overhead submerged arc welding and apparatus to implementthe same.

2. Description of the Related Art

A large amount of work in producing welded structures is taken up bycircumferential rotatable welds of hollow articles with limited accesson the inside to the joints being welded. The latter includecircumferential joints of closed vessels, reservoirs and housings,circumferential joints of pipelines, field welds and slots in the outerplating of ships' hulls; longitudinal welds of large-area articles whichare quite difficult to manouver into a position convenient for welding.They also include joints of panels which are difficult to manipulate,and also joints of segments, three-dimensional and flat sections etc.

The method of overhead submerged arc welding is characterized by thatthe weldpool, as compared with downhand submerged arc welding, is sortof turned by 180°, the flux and the electrode being fed in the verticalupward direction. Incidentally, the electrode is fed through a compactedlayer of flux.

That is why the method is called overhead welding.

It is also called the submerged arc welding, because the arc burns inthe thick of metal.

Such kind of welding produces so-called overhead welds.

Overhead welds may be of different types, e.g. overhead root welds andoverhead back-up welds. There may also be overhead single-pass welds andother types of overhead welds.

Overhead root welds are those which are the first to be run in welding ajoint and located in the upper part of the joints being welded on theside opposite to that of the electrode feed. Subsequent welding, i.e.making subsequent welds, is performed by any method known in the art,the electrode being fed from the same direction as in making overheadroot welds, e.g. internal root welds in circumferential rotatable jointsof vessels, reservoirs, connections of ships' outer bottom plating andother articles.

Overhead root arc welding makes it essentially possible to omitcircumferential rotatable welding inside vessels and welding in hardlyaccessible spaces in making rectilinear welds in structures with limitedaccess on the side opposite to the ceiling.

Overhead back-up welds are those which are the first to be run in makinga joint and located in the lower part of the sections being welded onthe side closest to that of the electrode feed. Subsequent welding isperformed by any method known in the art, with the electrode being fedfrom the side opposite to that compared with overhead root welding.

Root welds are practically used in welding overhead circumferential andlongitudinal joints of articles with limited access on the inside, andbackup welds are used in welding longitudinal joints of hardlymanoeuverable articles, e.g. sheet structures made of segments and otherarticles.

Overhead single-pass welds are those used in making limited-width jointsand located on the whole section being welded. Characteristically,subsequent welding of the joint on either side is not required.

Molding a ready-made weld presents many problems in making back-up andsingle pass welds.

In overhead welding, the molten flux and metal of the weldpool producedby burning of the arc as a result of melting of the welded metal,electrode material and welding flux are held from beneath by a crust ofpartially molten flux and by the action of molding devices. The lattermay be of different shapes and sizes and made in the form, for instance,of plates, shoes and back-up plates and other structural elements.

The flux is pressed from beneath to the welding spot, the expendedamount being constantly replenished in the welding process. To mold theupper portion of the weld, the flux may be fed both from the bottomthrough the gap between the edges of the article being welded and fromthe top, by any known method, with a loose layer of flux being formed inthe process. Back-up plates or flux-holding arrangements may also beused for the purpose.

The greatest number of problems arises in welding of large-size articleshaving the shape of a cylinder or approximating it, e.g. the hulls ofships and boiler unit casings, which require a particularly high qualityof welds and which must turn about their axes in the process of welding,and also in welding large-size flat articles which are difficult tohandle.

Known in the art is a method of overhead submerged arc welding (SU, A,469,554), whereby the flux and the electrode are fed from below thejoint, the flux pressure being adjusted all along the joint with the useof a special plate. The maximum flux pressure with the foregoing weldingmethod used is built up behind the arc.

With this method applied, however, the maximum flux pressure isregistered behind the arc at a distance larger than the length of theweldpool, which affects the welding process, as the weld metal graduallypresses of the adjusting plate.

Said prior art method is materialized in an apparatus, comprising ameans for feeding and pressing the flux to the welded article and awelding tip with a consumable electrode located inside the flux feedingmeans. The latter houses an adjusting plate, whose position is regulatedwith respect to the joint.

The operator using this apparatus observes the joint produced andadjusts the plate inclination angle to keep the requisite flux pressurein the event the joint forming parameters, e.g. the gap between theedges of the article, deviate from the standard. To obtain ahigh-quality overhead weld, it is essential to strictly keep to theprescribed flux pressure.

Welding with the use of said apparatus calls for constant change in theposition of the adjusting plate. This, in turn, requires the operator'sunremitting attention and a high professional level.

Thus, the quality of the weld being formed with the use of the aboveapparatus depends on the operator's skill and experience which is oftenconducive to impaired quality of the weld.

There is another prior art method of overhead submerged arc welding (DE,C, 3,125,225), whereby the flux is pressure-fed from below the joint, aconsumable electrode is fed to the joint through the flux from beneathand an arc is struck, whereupon a weldpool is formed and the joint iswelded with subsequent solidification of the weldpool and molding of theweld, and the flux is fed from below the joint with different pressuresapplied at different sections along the joint, the flux before the arcwith respect to the weld being formed is fed under a prescribed constantpressure essential for providing conditions favorable for pressing theweldpool, whereas on the section of arc burning and weldpool locationthe flux is supplied under a pressure necessary to keep the weldpool atthe level of the joint being welded, said pressure being constantlyincreased all along the weldpool so that the maximum flux pressure isapplied to the section of the beginning of the weld solidification.

Such a method of overhead submerged arc welding permits optimumdistribution of prescribed pressures on different sections along thejoint being welded, which makes it possible to reliably keep theweldpool at the level of the joint and form high-quality welds with therequisite reinforcement on the inside of the weld (on the side oppositeto the ceiling), e.i. in welding overhead root joints.

The welds thus made have deviations in the molding of the outside of thenewly-made weld in the form of unevenness, undercuts, local variationsin the weld width and other deviations.

Such deviations in the molding of the outside of the weld stem frominsufficient effect of the flux and the molding device on the weld inthe area of the beginning of the weld solidification, i.e. at the placeof the flux maximum pressure.

This method of overhead arc welding is materialized in an apparatus,comprising a means for feeding and pressing the flux to the joint beingwelded and a welding tip with a consumable electrode, placed inside themeans for feeding the flux, the inside of the means enclosing anadjusting plate adjustable with respect to the joint being welded tobuild up the requisite pressure in the area of the joint. The adjustingplate has a fold which divides it into two parts, "a" and "b", the foldbeing located under the section of the beginning of the weldsolidification to produce maximum flux pressure at the given section.The part "a" of the adjusting plate, located on the side of theweldpool, has a length practically equal to the length of the weldpooland is fitted under an angle α to the surface of the joint being welded,thereby assuring the requisite pressure of the flux upon the weldpool tokeep the latter at the level of the joint. The part "b" of the adjustingplate, located on the side of the weld being molded, extends to thesection of final molding of the weld and is fitted under an angle β tothe surface of the joint being welded to assure the requisite pressureupon the layer of liquid slag being fed on the section of the weldformation, from the maximum--in the area of the beginning of the weldsolidification, to the minimum--at the section of the final weldmolding.

Such an apparatus allows overhead welding to be carried out underoptimal process conditions, specifically, it makes it possible tocorrectly distribute and stabilize the prescribed pressure at eachindividual section, A, B, C along the joint being welded (before thearc, in the area of the arc and the weld-pool and in the location ofmolding a newly-made weld). However, at the section of the beginning ofsolidification, having a smaller length and actually presenting theboundary between the section B of the arc burning and the weldpool, andthe section C of the weld molding, deviations in the molding of theexternal side of the weld are due to insufficient effect at this sectionof the flat inclined section "a" of the adjusting plate, with the foldline thereof being located essentially at a distance equal to the lengthof the weldpool.

And as the section of the beginning of the weld molding (the boundary ofthe weldpool solidification) is arranged on the contour of the endportion of the weldpool, the flat section "a" located thereunder failsto ensure at the maximum flux pressure section a constant flux pressureall along this contour (boundary) of solidification.

This results in that in the process of welding at the section of themaximum flux pressure the pressure of the flux is uneven on the wholeboundary of the weldpool solidification, which gives rise to theforegoing unevenness, undercuts, and local variations in the weld widthand other deviations in the reinforcement on the outside of the weld.

The above-mentioned deviations in molding the external side of the weldhave an adverse effect upon the molding of the overhead weld as a whole,i.e. both on the inside and outside, and causes difficulties in themolding of welds whenever a very high quality of weld molding isrequired, e.g. in articles wherein the welds are subsequently coveredwith enamel, i.e. coated simultenaously with the entire article, etc.

SUMMARY OF THE INVENTION

The present invention aims to provide a method for overhead submergedarc welding and an apparatus to implement the same, in which throughselecting and distributing the pressure of flux at the boundary of thecrystallized weld it would be possible to ensure a high quality of anewly-made weld with the required high quality of reinforcement on bothsides of the weld.

The foregoing aim is accomplished by a method of overhead submerged arcwelding whereat is pressure-fed to the joint from below, through which aconsumable electrode is then fed from below, an arc is struck, aweldpool is formed and the joint is welded with subsequentsolidification of the weldpool and molding of a weld, the flux being fedat different pressures on different sections along the joint beingwelded, on the section before the arc relative to the weld being formedthe flux is fed under a constant prescribed pressure needed to provideconditions for pressuring the weldpool, and on the section of arcburning and weldpool location pressure is exercised through a layer offlux and a layer of liquid slag, which is gradually built up so that themaximum pressure of flux is applied to the section of the beginning ofthe solidification. According to the invention, the bulk of the flux ispressure-fed to the zone of the weldpool formation and the maximum fluxpressure formed thereat is distributed along the boundary of the sectionof the beginning of the weld solidification, the value of said pressurebeing maintained constant all along the boundary of solidification.

Such method of overhead arc welding allows correct feeding of the bulkof the flux to the zone of the weldpool formation, optimal production ofa maximum flux pressure distributed on the boundary of the section ofthe beginning of the weld solidification, and then maintenance of thevalue of said pressure at a constant level all along the boundary ofsolidification. All this promotes optimum conditions for performingoverhead welding at different sections along the joint being welded andmolding of high-quality welds.

Besides, implementing said method produces a positive effect on thestabilization of pre-assigned parameters of the process of overheadsubmerged arc welding, which makes it possible to obtain high-qualityoverhead welds.

Also, all operations in the method are simple to perform and easy to befully automated.

Welding in the optimum conditions with stable parameters of the processallows more rational use of welding materials, and is conductive totheir economy. Moreover, the pre-assigned requirements of the processare maintained with a high degree of accuracy.

It is expedient that in making back-up and single-pass welds the maximumflux pressure be distributed essentially on a parabola with the axis ofsymmetry thereof arranged in a vertical plane passing through thelongitudinal axis of symmetry of the weld.

This permits optimum concentration of the maximum flux pressure on theboundary of the section of the beginning of solidification, essentiallyapproximate it to the shape of the line of the weldpool solidification(in its tail part) and thus obtain optimum conditions for high-qualitymolding of overhead joints.

The foregoing object is also accomplished by an apparatus forimplementing the method, comprising a means for feeding and pressing theflux to the joint being welded, a welding tip with a consumableelectrode, located inside the means for feeding and pressing the flux tothe joint being welded, an adjusting plate to produce differentpressures on different sections along the joint being welded, the platebeing adjustable relative to the joint being welded inside the means forfeeding and pressing the flux to the joint being welded, the adjustingplate on the side of the joint being welded being made in the form oftwo intersecting sections, arranged at an angle to the joint beingwelded, with the apex thereof located under the section of the beginningof the weld solidification to produce the maximum flux pressure on saidsection, and a means for longitudinal displacement of the adjustingplate in the direction of welding in order to adjust the distancebetween the top of the adjusting plate and the welding tip. According tothe invention, the section of the adjusting plate located under theweldpool has a variable-section recess in the transverse andlongitudinal profiles with inclined walls to form and direct the flow offlux towards the zone of solidification of the weld-pool liquid metal,the edge of the recess facing the weldpool having a contour identicalwith the shape of the boundary of the weldpool solidification.

Such apparatus allows overhead welding to be performed under the optimumprocess conditions, i.e. it makes it possible to correctly distributeand stabilize the maximum flux pressure on the boundary of the weldsolidification, which ensures a substantially improved quality ofmolding of both sides of the weld.

Besides, this apparatus makes it possible to extend the range of usingthe method to articles different in purpose (e.g. those intended forenamelling), shape, dimensions and configuration of the joints beingwelded (e.g. with or without grooving).

The apparatus is easy to operate and can be handled by personnel withany proficiency standard.

Working practically in the automatic mode, such apparatus does notrequire special monitoring of the operation of its components.

Furthermore, the number of operations to be supervised by the operatoris considerably reduced.

All this makes it possible to substantially improve the quality ofwelded joints.

The apparatus is simple to manufacture, small in size and mass, andcomparatively cheap. Being able to maintain practically all weldingparameters at a constant level, the apparatus features higher weldingquality than the prior art apparatuses.

It is preferably that in making back-up and single-pass welds thesection of the adjusting plate arranged under the weldpool be providedwith a recess in the shape of a parabola.

It is also advisable that in making back-up and single-pass welds on thesection of the adjusting plate located under the weldpool twowedge-shaped intersecting projections be fitted, with the apices thereofarranged on the intersection of the inclined sections of the adjustingplate and having shaped cut-outs on their adjoining edges, forming onthe working surface of the adjusting plate a variable-section recesswith a cylindrical surface, tangent to the plane of said section of theadjusting plate on its generatrix and intersecting with the upper planesof the wedge-shaped projections on a parabola with the apex thereofarranged on the line of intersection of the inclined sections of theadjusting plate.

This permits optimum concentration of the flux maximum pressure on theboundary of the section of the beginning of the weld solidification,thereby favoring high-quality welds (particularly back-up andsingle-pass) through improvement in molding of reinforcement on bothsides of the weld.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in greater detail with reference toa specific embodiment thereof taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a schematic representation of an apparatus for overheadwelding, according to the invention (longitudinal section);

FIG. 2 is the section II--II in FIG. 1;

FIG. 3 is a diagram explaining the welding process (isometricprojection);

FIG. 4 shows an adjusting plate, an element of construction.

The method, according to the invention, will be described with referenceto FIGS. 1, 2 and 3, schematically showing the requisite elements of theapparatus to explain the method and the apparatus to implement the same.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The essence of the proposed method is as follows. For instance, flatmetal sheets 1 (FIG. 1) to be welded may be components of totallydifferent metal structures, e.g. a ship hull, which have limited accessfrom the top and may be welded only in the overhead position. To thisend, a flux 3 is fed and pressed by any method known in the art to thelocation of the joint to be welded with the aid of a means 2 for feedingand pressing the flux.

The inside of the means 2 houses a tip 4 (FIGS. 1, 2, 3) with aconsumable welding electrode 5. The welding electrode 5 may be of anyvariety widely used in industry, its type being irrelevant to theessence of the invention.

To initiate the welding process, it is necessary to feed the electrode 5to the joint to be welded, supply voltage to the electrode 5 (FIGS. 1,2) and strike an arc. The arc striken, the metal of the sheets 1, theflux 3 and the material of the electrode 5 melt, to produce a weldpool6.

Further action of the heat of the arc and the weldpool 6 promotessubsequent melting of the flux 3 and formation of liquid slag, a portionof which disposed under the weldpool 6, to form a so-called slag bath 7acted upon by the bulk of the flux 3 in the process of welding.

In keeping with the processes taking place, the whole of the weldingzone is technologically divided into several sections: a section Abefore the arc relative to a weld 8 being formed, a section B of the arcburning and location of the weldpool 6, which includes a section of thebeginning of solidification of the weld 8 and a section C of molding theweld 8.

The weld 8 in FIG. 3 is shown schematically.

The flux 3 (FIGS. 1, 2) is fed from below the joint to be welded underdifferent pressures on different sections A, B, C along the joint.

On the section A before the arc relative to the weld 8 being formed theflux is fed under a constant prescribed pressure essential for creatingconditions for pressing the weldpool 6. The pressure of the flux 3 onthe section A is preset on the basis of the welding mode chosen, theproperties and geometry of the material being welded and the shape ofthe joint. Besides, the pressure of the flux 3 on the section A is keptconstant.

On the section B, the bulk of the flux 3 is fed under a pressure capableof keeping the weldpool 6 at the level of the joint being welded, saidpressure being constantly built up all along the weldpool 6 in a mannerthat the maximum flux pressure is applied on the whole boundary of thesection of the beginning of solidification of the weld 8. The section ofthe beginning of solidification of the weld 8 is assumed to be thesection of the beginning of transition of the melt in the weldpool 6 tothe solid state, i.e. to the weld 8. The section of the beginning ofsolidification of the weld 8 is offset from the arc by a distance equalto the length of the weldpool (FIG. 1). The section of the beginning ofsolidification of the weld has a boundary which, on the side of thecrater on the lower surface of the joint being welded, shown in FIG. 3as a conventional plane 9, is arranged on a contour 10 and shaped as,for instance, a parabola. The vertex of such a parabola is also offsetfrom the arc by a distance equal to the length of the weld-pool, and itsaxis of symmetry is located in a vertical plane passing through thelongitudinal axis of symmetry of the weld.

The pre-assigned pressure on the section B is higher than that on thesection A.

Higher pressure on the section B is explained by the necessity tomaintain the melt in the weldpool 6 at the level of the joint beingwelded, considering the amount of flux which melts and cakes into acrust 11.

A layer of liquid slag is thereupon fed from below, out of the weldpool7, to the section C of weld molding, and pressure is applied thereto,said pressure varying from the maximum value on the section of thebeginning of solidification of the weld 8 to the minimum value on thesection C, whereon the layer of the liquid slag hardens to form a slagfilm 12 (FIGS. 1, 2), and the weld 8 is molded.

The maximum pressure on the section of the beginning of solidificationof the weld 8 is essential for maintaining the latter at the level ofthe joint being welded.

It is particularly important to apply and distribute the maximumpressure of the flux 3 on the boundary of the section of the beginningof solidification of the weld 8, as the molten metal in the weld-pool 6begins to solidify and becomes highly viscous on this boundary, therebyputting up maximum resistance to the pressure applied thereto.

It is noteworthy that the boundary of the section of the beginning ofsolidification of the weld is rather short; it is disposed on thecontour 10 and is actually the boundary of the solidification of theweld.

Of special importance, therefore, is the accuracy of applying maximumpressure of the flux 3 on the section of the beginning of solidificationof the weld 8, which must be applied on the boundary of the section ofthe beginning of solidification of the weld 8, as this considerablyaffects the quality of molding the weld 8, the more so that the positionof this boundary depends on the present welding parameters.

The contour 10 may be shaped, as, for instance, a parabola.

The value of the maximum pressure, established on the basis of thewelding conditions, the shape of the joint being welded and the materialof the article, must be constant on the entire contour 10, i.e. on theboundary shaped as, for instance, a parabola on the side of the crateron the lower surface of the joint being welded (sheets 1), actuallycoinciding with the conventional plane 9.

As the melt in the weldpool 6 passes to the solid state, i.e. to theweld 8, the pressure must gradually drop to minimum to mold the weld 8,simultaneously preserving the hardening slag layer, which forms the slagfilm 12 on the surface of the weld.

Pressure on the layer of the liquid slag fed from the slag bath 7 on thesection C of the molding of the weld 8 is exercised through a layer ofthe flux 3 distributed on the whole section C. This layer of slag fed onthe sections B and C serves as a lubricant between the metal of thesolidifying weld 8 and the flux layer, partially softened by thermalaction, through which pressure is applied.

Such lubricant in the form of a liquid slag layer helps maintain aconstant state of the weldpool 6 in performing a given type of overheadwelding, without mechanically breaking its equilibrium.

Besides, the pressure on the layer of liquid slag fed from the slag bath7 on the section C of molding the weld 8 may be exercised through aheat-removing molding surface 13 (FIG. 1).

The layer of liquid slag in this instance also plays the role of alubricant between the metal of the solidifying weld 8 and the moldingsurface 13. The heat-removing molding surface 13 speeds upsolidification of the weld 8, thereby adding to the capacity of thegiven method of overhead welding.

Use of the molding surface 13 presupposes that the pressure on the layerof the liquid slag on the section C of molding the weld 8 is exertedwithout a layer of the flux 3, which makes it possible to obtainhigh-quality welds of prescribed shapes.

The molding surface 13 is made of a material with a high heatconductivity, e.g. copper.

The molding surface 13 (FIG. 1) has a shaped working surface with theparameters thereof chosen proceeding from the permissible, both in shapeand dimensions, weld reinforcement section, the permissible variation inthe thickness of the liquid slag layer being fed, and the conditions forpassing of the solidifying weld 8 and formation, on both sides of theworking surface, of additional spaces to receive surplus flux 3.

To intensify heat removal from the welding zone, the molding surface 13may be cooled down by, for instance, water or air. Practically, suchmolding surface 13 may be made with the use of any molding device, e.g.a slider.

With this method of overhead submerged arc welding used, the bulk of theflux 3 is pressure-fed to the zone of formation of the weldpool 6.

Such concentration of the bulk of the flux 3 is essential for steadymaintenance of the melt in the weldpool 6 at the level of the lowersurface of the welded sheets 1 with the account taken on thecompensation for the amount of the flux 3 melting in thishigh-temperature zone, and for building up and distributing its maximumpressure on the boundary of the section of the beginning ofsolidification of the weld 8, i.e. on the contour 10.

With this method used, the value of this maximum pressure of the flux 3is kept constant all along the boundary of solidification of the weld 8.

The necessity for keeping a constant pressure of the flux 3 stems fromthe requirement to ensure constant conditions for pressing thesolidifying weld 8, particularly in the direction of its cross section,and thus to stabilize the prescribed welding conditions, which allowshigh-quality overhead welds to be obtained within a wide range oftechnological possibilities (as in the case of downhand submerged arcwelding).

In running back-up and single-pass welds with this method of weldingused, it is most advantageous to distribute the maximum pressure of theflux 3 on a parabola with the axis of symmetry thereof located in avertical plane passing through the longitudinal axis of symmetry of theweld 8, as a result of which the maximum pressure is actually applied onthe boundary of the section of the beginning of solidification of theweld 8, thus allowing high-quality welded joints to be obtained.

The proposed method is materialized in the following apparatus, which isshown in FIG. 1 as a tentative embodiment thereof.

The apparatus comprises a means 2 for feeding and pressing the flux tothe joint being welded from below.

Said means 2 may be any flux-feeding means known in the art, made, forinstance, in the form of a screw feeder widely used for the purpose(omitted in FIG. 1).

The apparatus is provided with a welding tip 4 with a consumableelectrode 5 located inside the means 2 for feeding and pressing theflux.

Basides, the apparatus incorporates an adjusting plate 14 with a moldingsurface 13, fitted inside the means 2 for feeding and pressing a flux 3and adjustable relative to a joint 1. Said adjusting plate 14 regulatesthe pressure of the flux 3 in the zone of the welded joint.

The adjusting plate 14 (FIGS. 3, 4) has a fold, forming a fold line 15.In the process of welding, the fold line 15 of the plate 14 is disposedunder the section of the beginning of solidification of a weld 8,forming a gap "f" between the top of the fold of the plate 14 and theweld 8 being molded.

The value of said gap "f" depends on the requisite shape of welds, typeof joints, properties of the material being welded and on the weldingconditions.

Owing to the arrangement of the fold line 15 of the adjusting plate 14under the section of the beginning of solidification of the weld 8,maximum pressure of the flux 3 (FIGS. 1, 2) is produced on this section.

The above-mentioned part "a" of the adjusting plate 14, located on theside of a weldpool 6 has a length essentially equal to the length of theweldpool 6; said part "a" is fitted under an angle "α" to the surface ofthe joint, ensuring the requisite pressure of the flux 3 on the weldpool6 to keep the latter at the level of the joint being welded.

The foregoing part "b" of the adjusting plate 14 located on the side ofthe weld 8 being molded extends to the place of final molding of theweld 8; said part "b" is disposed at an angle "β" to the surface of thejoint, ensuring pressure on the layer of liquid slag being fed on thesection C of molding the weld 8 from the maximum value on the section ofthe beginning of solidification of the weld 8 to the minimum value onthe section of final molding of the weld 8.

For effectively shaping and directing the bulk of the flux 3 to the zoneof solidification of the weldpool 6, the portion "a" of the adjustingplate 14 located under the weldpool 6 has a variable-section recess inthe longitudinal and transverse profiles with inclined walls. The recessedge 16 facing the weldpool 6 has a contour coinciding with the shape ofthe contour 10 of solidification of the weldpool 6, i.e. with the shapeof the boundary of the section of the beginning of solidification of theweld 8.

In running back-up and single-pass welds on the portion "a" of theadjusting plate 14, it is preferable to make, e.g. by soldering, twowedge-shaped projections 18, contacting each other on a line 17, locatedon the intersection of the inclined sections "a" and "b" of theadjusting plate 14, i.e. on the fold line 15 of the plate 14.

The wedge-shaped projections 18 have shaped cutouts on their adjacentedges, which form on the working surface of the plate 14 avariable-section recess, e.g. a surface with a cylindrical surface,tangent to the plane of the section "a" of the adjusting plate 14 on itscontact line 17.

The cylindrical surface of this recess intersects with the upper planesof the wedge-shaped projections 18 on the edge 16 of the recess,representing a parabola.

The vertex of the parabola is located on the intersection (fold) line 15of the inclined sections of the adjusting plate 14.

In making root and other types of overhead welds, especially with theuse of grooving, recesses and corresponding projections on the adjustingplate 14 may have different shapes, depending on the specific weldingconditions.

The dimensions and shapes of such recesses are selected on the basis ofthe welding mode, shape of the joint (e.g. with or without grooving),the requisite weld reinforcement shape etc.

Structurally, a groove, e.g. one with a cylindrical surface,intersecting with the upper plane of the wedge-shaped projections 18 onthe parabola, creates conditions whereat any longitudinal verticalsection plane of the working surface of the adjusting plate 14 formsintersection lines disposed at equal angles "α" (FIGS. 1, 3) and whosevalue is equal to

    α=180°-(α+β)°

Such conditions of constant interaction of the working surface of theadjusting plate 14 on the section of the maximum pressure of the flux 3helps form high-quality welds in general.

Incidentally, the recess on the section "a" of the adjusting plate 14 isdisposed under the contour 10 of the tail portion of the weldpool 6 onthe side of the crater on the lower surface of the joint being welded,i.e. under the boundary of the section of solidification of the weld ina manner that the apex of the contour 10 of the beginning ofsolidification of the weld 8 is under the vertex of the parabola formedby the edges of the recess.

Such mutual position during welding of the contour 10 and the parabolaensure optimum shaping and distribution of a constant prescribed maximumpressure of the flux 3 on the whole boundary of the section of thebeginning of solidification of the weldpool 6 and, consequently,improves the quality of welding due to a better reinforcement molding onboth sides of the weld 8.

For a more accurate tuning to the prescribed welding mode, the apparatusmay be provided with a means for longitudinal displacement of theadjusting plate 14 in the direction of welding (not illustrated). Such ameans is preferable in adjusting the distance between the fold line 15of the adjusting plate and the welding tip 4. Besides, such a meansmakes it possible to perform welding, strictly observing therequirements made on the method of overhead welding, which contributesto a higher quality of overhead welds in general.

Maximum effect from using the method and apparatus to implement thesame, according to the invention, is derived in running back-up andsingle-pass welds in cases requiring a high quality of molding thereinforcement surface both on the outer and inner sides of the jointbeing welded (e.g. circumferential welds of reservoirs, pipelines,vessels, housings or longitudinal welds of three-dimensional sections,panels, segments etc.).

On the whole, the apparatus and the method, according to the invention,permit automatic welding of overhead welds with a higher quality ofmolding the surface of both sides of the welds and a considerably highercapacity of overhead welding than that obtained with the use of priorart devices, and allows high-quality overhead welds to be produced.

We claim:
 1. A method of overhead submerged arc welding, comprising thesteps of:pressure-feeding flux to a joint being welded from below;feeding a consumable electrode through the flux from below to the jointbeing welded; striking an arc; forming a weldpool; welding the jointwith subsequent solidification of the weldpool to form a weld; moldingthe weld, the flux being fed at different pressure on different sectionsalong the joint being welded, so that a first section before the arcrelative to the weld being formed is fed under a constant prescribedpressure needed to provide conditions for pressuring the weldpool, asecond section of arc burning and location of the weldpool is subjectedto a pressure through a layer of flux and a layer of liquid slag, whichis gradually built up so that maximum pressure of flux is applied to anarea of beginning of weld solidifaction, wherein a bulk of the flux ispressure fed to a zone of formation of the weldpool and maximum fluxpressure is distributed along a boundary of the area of weldsolidification, the maximum flux pressure being maintained constantalong the boundary of solidification.
 2. A method as claimed in claim 1,wherein, in making back-up and single-pass welds, the maximum fluxpressure is distributed essentially on a parabola with an axis ofsymmetry arranged in a vertical plane passing through a longitudinalaxis of symmetry of the weld.
 3. An apparatus for implementing a methodof overhead submerged arc welding , comprising: a means for feeding andpressing flux to a joint being welded, a welding tip with a consumableelectrode, located inside the means for feeding and pressing the flux tothe joint being welded, an adjusting plate to produce differentpressures on different sections along the joint being welded, adjustablerelative to the joint being welded, the adjusting plate on the side ofthe joint being made in the form of two intersection sections, arrangedat an angle to the joint being welded, with an apex thereof locatedunder a section of beginning of weld solidification to produce a maximumflux pressure on said section, a means for longitudinal displacement ofthe adjusting plate in a direction of welding in order to adjust adistance between a top of the adjusting plate and the welding tip, asection of the adjusting plate located under a weldpool having avariable cross-section recess in transverse and longitudinal profileswith inclined walls to form and direct a flow of flux towards a zone ofsolidification of weldpool liquid metal, an edge of the recess facingthe weldpool having a contour identical with the shape of the boundaryof weldpool solidification.
 4. An apparatus for implementing a method ofoverhead submerged arc welding as claimed in claim 3, wherein, formaking back-up and single-pass welds, the recess is shaped as aparabola.
 5. An apparatus for implementing a method of overheadsubmerged arc welding as claimed in claim 4, wherein, in making back-upand single-pass welds, two wedge-shaped intersecting projections arefitted on the section of the adjusting plate located under the weldpool,apices of the projections being arranged on the intersection of theinclined sections of the adjusting plate and having shaped cutouts onadjoining edges, forming on a working surface of the adjusting plate avariable cross-section recess with a cylindrical surface, tangent to aplane of said section of the adjusting plate.